JEjerf·Apr 16, 2021
That is a good idea, but one thing I would advise, having both seen several attempts made at this sort of thing and having made one myself [1], try very hard to separate the accidental things Erlang brings to the idea from the fundamental things Erlang brings to the idea. Most attempts I've seen made at this flounder on this pretty hard by trying to port too directly the exact Erlang supervisor tree idea while grinding hard against the rest of the language, rather than porting the core functionality in in a way that integrates natively with the language in question as much as possible.
For instance, one thing I found when I was writing my library that will probably apply to most other languages (probably including Rust) is that Erlang has a somewhat complicated setup step for running a gen_server, with an explicit setup call, a separate e
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xecution call, several bits and pieces for 'officially' communicating with a gen_server, etc. But a lot of these things are for dealing with the exact ways that Erlang interacts with processes, and you probably don't need most of them. Simply asking for a process that makes the subprocess "start" from scratch is probably enough, and letting that process use existing communication mechanisms already in the language rather than trying to directly port the Erlang stuff. Similarly, I found no value in trying to provide direct ports of all the different types of gen_server, which aren't so much about the supervision trees (even if that's where they seem to be located) as a set of standard APIs for working with those various things. They're superfluous in a language that already has other solutions for those problems.
In addition to keeping an eye out for features you don't need from Erlang, keep an eye out for features in the host language that may be useful; e.g., the most recent suture integrates with the Go ecosystem's ever-increasing use of context.Contexts as a way to manage termination, which hasn't got a clear Erlang equivalent. (Linking to processes has some overlapping functionality but isn't exactly the same, both offering some additional functionality contexts don't have as well as missing some functionality contexts do have.)
Erlang has a lot of good ideas that I'd love to see ported into more languages. But a lot of attempts to do so flounder on these issues, creating libraries so foreign to the host language that they have zero chance of uptake.
The other thing I'd point out is that even in Go, to say nothing of Rust, crashing is actually fairly uncommon by Erlang standards. Many things that crash in Erlang are statically prevented at compile time in Go, and Rust statically precludes even more of them. However, I have found it OTP-esque supervision trees to be a very nice organizational structure to my code; I use suture in nearly every non-trivial Go program I write because it makes for a really nice modular approach for the question of "how do I start and stop persistent services?". I have seen it hold together runtime services that would otherwise be failing, the way it is supposed to, and that's nice, but the organization structure is still probably the larger benefit.
(There is deep reason for the way Erlang is doing it the way it does, which is that a lot of Erlang's type system, or lack thereof, is for communicating between nodes, so even if you perfectly program Erlang, if two nodes running different versions of code try to communicate with each other and they've changed the protocol you might get a pattern matching fail on the messages flowing between versions. The Erlang way of doing cross-machine communication with this sort of automatic serialization at the language level has not caught on, and all modern languages have a relatively distinct serialization step where this sort of error is better handled, as you try to deserialize the remote message into your internal data structure.)
Anyhow, the upshot is, you want to translate the functionality out of Erlang into other languages, not transliterate it.
[1]: https://github.com/thejerf/suture